Modified boot.img to go with cm-12.1-20160819-UNOFFICIAL-m4.zip by Wingman2K.
Memory improvements:
ZRAM and swap enabled in the kernel.
Unnecessary kernel option switched off to save a little on kernel size.
Swapping to ZRAM, ro.config.low_ram=true, disabled JIT and KSM options as per https://source.android.com/devices/tech/config/low-ram.
Battery charging:
Limit battery charge to 90%. This will make your battery last a lot longer. (Google for "battery university").